Power control method and system for three-phase voltage unbalance treatment of power distribution network

Abstract

The invention discloses a power control method and system for three-phase voltage unbalance treatment of a power distribution network. Based on a three-phase unbalanced power flow algorithm, considering active power of a single-phase distributed photovoltaic, performing three-phase power flow calculation on the power distribution network containing the distributed photovoltaic to obtain a Jacobian matrix, and determining a relationship between power change of each node and voltage amplitude and phase change; constructing a three-phase voltage unbalance coefficient sensitivity matrix, and determining the response of the node voltage and the three-phase voltage unbalance coefficient to reactive power injection; and according to the three-phase voltage unbalance coefficient sensitivity matrix, taking node voltage deviation and voltage unbalance coefficient minimization as optimization objectives, determining an optimal reactive power scheduling objective function and constraint conditions for the three-phase voltage unbalance treatment of the power distribution network, and establishing a power optimization control model for the three-phase voltage unbalance treatment of the power distribution network. The distributed photovoltaic optimal reactive power output method has the advantages of being low in cost, high in flexibility, easy to integrate and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network operation control, and in particular to a power control method and system for managing three-phase voltage imbalance in a distribution network. Background Art

[0002] With the rapid development of distributed energy technologies, such as photovoltaic systems, small wind power systems and fuel cells, they have been widely used in distribution networks. For distribution networks containing distributed resources, voltage imbalance is common due to many factors, such as unbalanced distribution of single-phase loads, incomplete transposition of transmission lines and cables, etc. In addition, the random installation of distribution devices, such as rooftop photovoltaics, is randomly installed without reasonable planning, which makes the three-phase voltage imbalance problem of distribution networks frequent.

[0003] At present, there are two main methods to alleviate the voltage imbalance problem in the distribution network: the first method is to use the existing equipment in the distribution network, such as on-load tap-changer transformers, voltage regulators and switch capacitors; however, the tap position of the on-load tap-changer transformer cannot be changed frequently, otherwise its service life will be shortened, and the voltage regulator and switch capacitor may introduce unstable operating points for the distribution network. The second method is to use power electronic equipment, such as shunt static VAR compensators and distribution static synchronous compensators, but the installation cost is high. Summary of the invention

[0004] The present invention provides a power control method and system for managing three-phase voltage imbalance in a distribution network, which has the advantages of low cost, high flexibility, easy integration, etc.

[0005] The present invention provides a power control method for managing three-phase voltage imbalance in a power distribution network, comprising:

[0006] Calculate the three-phase power flow of the distribution network, obtain the Jacobian matrix, and determine the relationship between the power change of each node and the voltage amplitude and phase change in, is the Jacobian matrix, ΔP is the active power change of each node, ΔQ is the reactive power change of each node, ΔE is the voltage amplitude change of each node, and ΔF is the phase change of each node;

[0007] Substitute the above equation (1) into the equation of the change ΔVUF of the three-phase voltage unbalance coefficient and the change ΔV of the voltage at all nodes: Get the three-phase voltage unbalance coefficient sensitivity matrix

[0008] in, is the three-phase voltage unbalance coefficient sensitivity matrix for all node voltage changes, is the three-phase voltage unbalance coefficient sensitivity matrix for all node active power and reactive power, and The three-phase voltage unbalance coefficient sensitivity matrix corresponding to active power and reactive power injection of all nodes respectively;

[0009] Assuming that the active power injected by the single-phase distributed photovoltaic in the distribution network is constant, and only the reactive power of the single-phase distributed photovoltaic can be controlled, the relationship (3) is simplified to Where ΔQ is the reactive power injection of all nodes;

[0010] Establish the relationship between the reactive power injection of all nodes and the reactive power injection of single-phase distributed photovoltaics ΔQ=DΔQ DER (5); where ΔQ DER is the reactive power injection of all single-phase distributed photovoltaics, and D is N showing the connection relationship between single-phase distributed photovoltaics and nodes. T ×N d Incidence matrix, N d is the number of single-phase distributed photovoltaics, N T is the number of single-phase nodes;

[0011] Substituting the relation (5) into the relation (4), the relation between the change vector of the three-phase voltage unbalance coefficient and the reactive power injection of the single-phase distributed photovoltaic is obtained:

[0012] Based on the relationship (6), the objective function of the three-phase voltage unbalance coefficient is constructed: Taking the minimum voltage deviation of each node in the distribution network as the optimization goal, the node voltage deviation objective function is constructed Among them, VUF orig is the three-phase voltage unbalance coefficient vector of all three-phase nodes before reactive power injection, p is the phase of the node, ΔV i p is the voltage deviation on a phase at node i during composite power injection, ||·||1 is the Manhattan norm;

[0013] Assuming that the active power injected by the single-phase distributed photovoltaic in the distribution network is constant and only the reactive power of the single-phase distributed photovoltaic can be controlled, the objective function of the optimal reactive power output of the distributed photovoltaic for the three-phase voltage imbalance management of the distribution network is constructed with the minimization of the node voltage deviation and the voltage imbalance coefficient as the optimization goal, minω1J1+ω2J2(9); where ω1 and ω2 are the weight factors of the three-phase voltage imbalance coefficient objective function and the node voltage deviation objective function respectively;

[0014] The voltage constraint of the distribution network node is V min ≤|V ip |≤V max (10): where v min and v max are the voltage upper and lower limits of the distribution network nodes respectively; the reactive power constraint of single-phase distributed photovoltaic is constructed as: In the above formula, and are the upper and lower limits of the reactive power output of single-phase distributed photovoltaics, respectively. DERi is the rated capacity of single-phase distributed photovoltaic, P DERi It is the active power output of single-phase distributed photovoltaic;

[0015] Based on the objective function, voltage constraint and reactive power constraint, a power optimization control model for managing three-phase voltage imbalance in distribution network is constructed, and the power optimization control model for managing three-phase voltage imbalance in distribution network is solved to obtain the optimal reactive output of distributed photovoltaic.

[0016] Specifically, based on the objective function, voltage constraint and reactive power constraint, a power optimization control model for the three-phase voltage unbalance management of the distribution network is constructed, and the power optimization control model for the three-phase voltage unbalance management of the distribution network is solved to obtain the optimal reactive power output of the distributed photovoltaic system, including:

[0017] Based on the quadratic convex approximation method, the power optimization control model for the three-phase voltage imbalance management of the distribution network is processed non-convexly to obtain a new distributed photovoltaic optimal reactive power output objective function for the three-phase voltage imbalance management of the distribution network.

[0018] Based on the reactive disturbance of single-phase distributed photovoltaic, the voltage deviation of all nodes can be estimated as in, are two parts of the voltage sensitivity matrix in equation (3), which respectively represent the sensitivity of node voltage amplitude and phase to reactive power change; based on equations (7), (8) and (13), equation (12) is converted into the objective function in, and

[0019] Establishing linearized node voltage constraints and Among them, K 1i and K 2i is the linear approximation constant of the node voltage constraint, E i is the voltage amplitude component at node i, F i is the voltage phase component at node i, is the maximum permissible value of the square of the voltage at node i, is the minimum permissible value of the square of the voltage at node i;

[0020] Based on the relationship (14), the objective function of the quadratic problem of distributed photovoltaic optimal reactive output for three-phase voltage imbalance control in distribution network is obtained: Among them, H=ω1H1+ω2H2, is the voltage amplitude sensitivity matrix for reactive power injection at all nodes, is the three-phase voltage unbalance coefficient sensitivity matrix for reactive power injection at all nodes;

[0021] Based on the relationships (11), (15), (16) and (17), a convex optimization model of power optimization control for the management of three-phase voltage imbalance in distribution network is constructed. The convex optimization model of power optimization control for the management of three-phase voltage imbalance in distribution network is solved to obtain the optimal reactive power output of distributed photovoltaic power generation.

[0022] Specifically, the power optimization control convex optimization model for the three-phase voltage imbalance management of the distribution network is solved to obtain the optimal reactive power output of the distributed photovoltaic system, including:

[0023] Based on the optimization algorithm, the power optimization control convex optimization model for the three-phase voltage imbalance management of the distribution network is solved. If the VUF of all three-phase nodes cannot meet the preset requirements after optimization, the weight factors ω1 and ω2 are updated until the VUE of all nodes meet the preset requirements, and the optimal reactive output of distributed photovoltaics is obtained.

[0024] The present invention also provides a power control system for managing three-phase voltage imbalance in a power distribution network, comprising:

[0025] The three-phase power flow calculation module is used to calculate the three-phase power flow of the distribution network, obtain the Jacobian matrix, and determine the relationship between the power change of each node and the voltage amplitude and phase change. in, is the Jacobian matrix, ΔP is the active power change of each node, ΔQ is the reactive power change of each node, ΔE is the voltage amplitude change of each node, and ΔF is the phase change of each node;

[0026] The three-phase voltage unbalance coefficient sensitivity matrix acquisition module is used to substitute the relationship (1) into the relationship between the change ΔVUF of the three-phase voltage unbalance coefficient and the change ΔV of the voltage at all nodes. Get the three-phase voltage unbalance coefficient sensitivity matrix in, is the three-phase voltage unbalance coefficient sensitivity matrix for all node voltage changes, is the three-phase voltage unbalance coefficient sensitivity matrix for all node active power and reactive power, and The three-phase voltage unbalance coefficient sensitivity matrix corresponding to active power and reactive power injection of all nodes respectively;

[0027] The three-phase voltage unbalance coefficient sensitivity matrix simplification module is used to assume that the active power injected by the single-phase distributed photovoltaic in the distribution network is constant and only the reactive power of the single-phase distributed photovoltaic can be controlled, and the relationship (3) is simplified to Where ΔQ is the reactive power injection of all nodes;

[0028] The three-phase voltage unbalance coefficient sensitivity matrix conversion module is used to establish the relationship between the reactive power injection of all nodes and the reactive power injection of single-phase distributed photovoltaics ΔQ=DΔQ DER (5); where ΔQ DER is the reactive power injection of all single-phase distributed photovoltaics, and D is N showing the connection relationship between single-phase distributed photovoltaics and nodes. T ×N d Incidence matrix, N d is the number of single-phase distributed photovoltaics, N T is the number of single-phase nodes; Substituting the relation (5) into the relation (4), the relation between the change vector of the three-phase voltage unbalance coefficient and the reactive power injection of the single-phase distributed photovoltaic is obtained:

[0029] An objective function construction module is used to construct an objective function of the three-phase voltage unbalance coefficient based on the relation (6). Taking the minimum voltage deviation of each node in the distribution network as the optimization goal, the node voltage deviation objective function is constructed Among them, VUF orig is the three-phase voltage unbalance coefficient vector of all three-phase nodes before reactive power injection, p is the phase of the node, ΔV i p is the voltage deviation on a certain phase at node i when composite power is injected, and ||·||1 is the Manhattan norm. Assuming that the active power injected by the single-phase distributed photovoltaic in the distribution network is constant and only the reactive power of the single-phase distributed photovoltaic can be controlled, the node voltage deviation and the voltage imbalance coefficient are minimized as the optimization objectives, and the objective function of the optimal reactive output of distributed photovoltaic for the three-phase voltage imbalance management of the distribution network is constructed as minω1J1+ω2J2(9); where ω1 and ω2 are the weight factors of the three-phase voltage imbalance coefficient objective function and the node voltage deviation objective function, respectively.

[0030] Constraint building module, used to build the voltage constraint of the distribution network node as V min ≤|V i p |≤V max (10): where v min and v max are the voltage upper and lower limits of the distribution network nodes respectively; the reactive power constraint of single-phase distributed photovoltaic is constructed as: In the above formula, and are the upper and lower limits of the reactive power output of single-phase distributed photovoltaics, respectively. DERi is the rated capacity of single-phase distributed photovoltaic, P DERi It is the active power output of single-phase distributed photovoltaic;

[0031] The power control module is used to construct a power optimization control model for the management of three-phase voltage imbalance in the distribution network based on the objective function, voltage constraints and reactive power constraints, solve the power optimization control model for the management of three-phase voltage imbalance in the distribution network, and obtain the optimal reactive power output of distributed photovoltaics.

[0032] Specifically, the power control module includes:

[0033] A non-convex processing unit is used to perform non-convex processing on the power optimization control model for the three-phase voltage imbalance management of the distribution network based on the quadratic convex approximation method, so as to obtain a new distributed photovoltaic optimal reactive power output objective function for the three-phase voltage imbalance management of the distribution network.

[0034] The objective function conversion unit is used for reactive disturbance based on single-phase distributed photovoltaics. The voltage deviation of all nodes can be estimated as in, are two parts of the voltage sensitivity matrix in equation (3), which respectively represent the sensitivity of node voltage amplitude and phase to reactive power change; based on equations (7), (8) and (13), equation (12) is converted into the objective function in, and

[0035] Voltage constraint establishment unit, used to establish linearized node voltage constraints and Among them, K 1i and K 2i is the linear approximation constant of the node voltage constraint, E i is the voltage amplitude component at node i, F i is the voltage phase component at node i, is the maximum permissible value of the square of the voltage at node i, is the minimum permissible value of the square of the voltage at node i;

[0036] The final objective function obtaining unit is used to obtain the objective function of the quadratic problem of the optimal reactive power output of distributed photovoltaic power generation for the three-phase voltage imbalance control of the distribution network based on the relation (14). Among them, H=ω1H1+ω2H2, is the voltage amplitude sensitivity matrix for reactive power injection at all nodes, is the three-phase voltage unbalance coefficient sensitivity matrix for reactive power injection at all nodes;

[0037] A power control unit is used to construct a convex optimization model of power optimization control for three-phase voltage imbalance management in a distribution network based on the relationships (11), (15), (16) and (17), solve the convex optimization model of power optimization control for three-phase voltage imbalance management in a distribution network, and obtain the optimal reactive power output of distributed photovoltaics.

[0038] Specifically, the power control unit includes:

[0039] A convex optimization model construction subunit is used to construct a power optimization control convex optimization model for three-phase voltage imbalance management in a distribution network based on the above-mentioned equations (11), (15), (16) and (17);

[0040] The power control execution subunit is used to solve the power optimization control convex optimization model for the three-phase voltage imbalance management of the distribution network based on the optimization algorithm. If the VUF of all three-phase nodes cannot meet the preset requirements after optimization, the weight factors ω1 and ω2 are updated until the VUE of all nodes meet the preset requirements, thereby obtaining the optimal reactive power output of the distributed photovoltaic.

[0041] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:

[0042] 1. First, obtain the data of the distribution network containing distributed photovoltaics. Based on the three-phase unbalanced power flow algorithm, consider the active power of single-phase distributed photovoltaics, calculate the three-phase power flow of the distribution network containing distributed photovoltaics, obtain the Jacobian matrix, and determine the relationship between the power change of each node and the voltage amplitude and phase change; according to the relationship between the power change of each node and the voltage amplitude and phase change, construct the three-phase voltage unbalance coefficient sensitivity matrix to determine the response of the node voltage and the three-phase voltage unbalance coefficient to reactive power injection; according to the three-phase voltage unbalance coefficient sensitivity matrix, take the minimization of node voltage deviation and voltage unbalance coefficient as the optimization goal, determine the optimal reactive power dispatch objective function and constraint conditions for the three-phase voltage unbalance management of the distribution network, and establish a power optimization control model for the three-phase voltage unbalance management of the distribution network. Solve the power optimization control model for the three-phase voltage unbalance management of the distribution network to obtain the optimal reactive output of distributed photovoltaics, which has the advantages of low cost, high flexibility, and easy integration.

[0043] 2. Based on the quadratic convex approximation method, the power optimization control model for the three-phase voltage imbalance management in the distribution network is processed non-convexly, the objective function and linear constraints of the quadratic problem are determined, and an easy-to-solve convex optimization model of power optimization control for the three-phase voltage imbalance management in the distribution network is obtained. The optimal power flow problem is converted into an easy-to-solve quadratic optimization problem with faster calculation speed, which can realize short-term reactive power scheduling of multi-node distribution networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic diagram of a power control method for managing three-phase voltage imbalance in a distribution network provided by an embodiment of the present invention;

[0045] Figure 2 A module diagram of a power control system for managing three-phase voltage imbalance in a distribution network provided by an embodiment of the present invention;

[0046] Figure 3 A topological diagram of a 13-node IEEE distribution network containing multiple single-phase distributed photovoltaics in an embodiment of the present invention;

[0047] Figure 4 A single-phase distributed photovoltaic active power curve diagram in an embodiment of the present invention;

[0048] Figure 5 This is a comparison diagram of the node #692VUF distribution before and after optimization of single-phase distributed photovoltaic reactive power scheduling in an embodiment of the present invention;

[0049] Figure 6 It is a 24-hour VUF distribution diagram of all nodes before single-phase distributed photovoltaic reactive power scheduling optimization in an embodiment of the present invention;

[0050] Figure 7It is a 24-hour VUF distribution diagram of all nodes after the single-phase distributed photovoltaic reactive power scheduling optimization in an embodiment of the present invention;

[0051] Figure 8 It is a 24-hour voltage distribution diagram of all nodes before single-phase distributed photovoltaic reactive power scheduling optimization in an embodiment of the present invention;

[0052] Fig. 9 This is a 24-hour voltage distribution diagram of all nodes after single-phase distributed photovoltaic reactive power scheduling optimization in an embodiment of the present invention. DETAILED DESCRIPTION

[0053] The embodiment of the present invention provides a power control method and system for managing three-phase voltage imbalance in a distribution network, which has the advantages of low cost, high flexibility, and easy integration.

[0054] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0055] like Figure 1 As shown, the power control method for managing three-phase voltage imbalance in a distribution network provided by an embodiment of the present invention includes:

[0056] Step S110: Calculate the three-phase power flow of the distribution network to obtain the Jacobian matrix and determine the relationship between the power change of each node and the voltage amplitude and phase change. in, is the Jacobian matrix, ΔP is the active power change of each node, ΔQ is the reactive power change of each node, ΔE is the voltage amplitude change of each node, and ΔF is the phase change of each node;

[0057] Before step S110, the distribution network data is obtained. In this embodiment, the distribution network data includes voltage measurement data, active power and reactive power data of each node, upper and lower limits of reactive power of each single-phase distributed photovoltaic inverter, and upper and lower voltage limits of all nodes.

[0058] Step S120: Substitute equation (1) into the equation of the change ΔVUF of the three-phase voltage unbalance coefficient and the change ΔV of the voltage at all nodes: Get the three-phase voltage unbalance coefficient sensitivity matrix in, is the three-phase voltage unbalance coefficient sensitivity matrix for all node voltage changes, is the three-phase voltage unbalance coefficient sensitivity matrix for all node active power and reactive power, and The three-phase voltage unbalance coefficient sensitivity matrix corresponding to active power and reactive power injection of all nodes respectively;

[0059] Specifically, the three-phase voltage at node k can be expressed as follows:

[0060]

[0061] in, They represent the three-phase voltages a, b, and c at node k, respectively. Respectively represent the amplitude of the three-phase voltage a, b, c, Represent the phases of the three-phase voltages a, b, and c respectively; the voltage vector at node k is decomposed as follows:

[0062]

[0063] The expression of three-phase voltage unbalance coefficient is:

[0064]

[0065] Among them, α is a complex number, which represents the phase difference between the phase voltages, and the expression is:

[0066]

[0067] Assume that the voltage at node k is V k Based on formula (c), the change of the three-phase voltage unbalance coefficient at node k can be obtained, and the expression is:

[0068]

[0069] in, is the three-phase voltage unbalance coefficient sensitivity matrix with respect to the voltage change at node k, and f represents the VUF function in (c). Based on (e), the three-phase voltage unbalance coefficient change matrix of all three-phase nodes is obtained as follows:

[0070]

[0071] Where, ΔV k represents the voltage change at node k, ΔVUF k represents the change in the three-phase voltage unbalance coefficient corresponding to the voltage change at node k, O 1×6 is the zero vector, N 3φ and N T are the number of three-phase nodes and the number of single-phase nodes in the distribution network, respectively;

[0072] Simplifying equation (f), we can get the relationship between ΔVUF and ΔV at all nodes:

[0073] Step S130: Assuming that the active power injected by the single-phase distributed photovoltaic in the distribution network is constant, only the reactive power of the single-phase distributed photovoltaic can be controlled, the relationship (3) is simplified to Where ΔQ is the reactive power injection of all nodes;

[0074] Step S140: Establish the relationship between the reactive power injection of all nodes and the reactive power injection of single-phase distributed photovoltaic: ΔQ=DΔQ DER (5); where ΔQ DER is the reactive power injection of all single-phase distributed photovoltaics, and D is N showing the connection relationship between single-phase distributed photovoltaics and nodes. T ×N d Incidence matrix, N d is the number of single-phase distributed photovoltaics, N T is the number of single-phase nodes;

[0075] Step S150: Substitute equation (5) into equation (4) to obtain the relationship between the three-phase voltage unbalance coefficient change vector and the reactive power injection of the single-phase distributed photovoltaic

[0076] Step S160: Based on equation (6), construct the objective function of the three-phase voltage unbalance coefficient Taking the minimum voltage deviation of each node in the distribution network as the optimization goal, the node voltage deviation objective function is constructed Among them, VUF orig is the three-phase voltage unbalance coefficient vector of all three-phase nodes before reactive power injection, p is the phase of the node, ΔV i p is the voltage deviation of a phase (p phase) at node i during composite power injection, and ||·||1 is the Manhattan norm;

[0077] Step S170: Assuming that the active power injected by the single-phase distributed photovoltaic in the distribution network is constant and only the reactive power of the single-phase distributed photovoltaic can be controlled, the objective function minω1J1+ω2J2(9) of the optimal reactive power output of distributed photovoltaic for the three-phase voltage imbalance management of the distribution network is constructed with the minimization of the node voltage deviation and the voltage imbalance coefficient as the optimization target; wherein ω1 and ω2 are the weight factors of the three-phase voltage imbalance coefficient objective function and the node voltage deviation objective function respectively;

[0078] Step S180: Construct the voltage constraint of the distribution network node as V min ≤|V i p |≤V max (10): where v min and v maxare the voltage upper and lower limits of the distribution network nodes respectively; the reactive power constraint of single-phase distributed photovoltaic is constructed as: In the above formula, and are the upper and lower limits of the reactive power output of single-phase distributed photovoltaics, respectively. DERi is the rated capacity of single-phase distributed photovoltaic, P DERi It is the active power output of single-phase distributed photovoltaic;

[0079] Step S190: Based on the objective function, voltage constraints and reactive power constraints, a power optimization control model for the management of three-phase voltage imbalance in the distribution network is constructed, and the power optimization control model for the management of three-phase voltage imbalance in the distribution network is solved to obtain the optimal reactive power output of distributed photovoltaics.

[0080] This step is specifically described. Based on the objective function, voltage constraint and reactive power constraint, a power optimization control model for the three-phase voltage imbalance management of the distribution network is constructed. The power optimization control model for the three-phase voltage imbalance management of the distribution network is solved to obtain the optimal reactive power output of the distributed photovoltaic system, including:

[0081] Based on the quadratic convex approximation method, the power optimization control model for the three-phase voltage imbalance management of the distribution network is processed non-convexly, and a new distributed photovoltaic optimal reactive power output objective function for the three-phase voltage imbalance management of the distribution network is obtained.

[0082] Based on the reactive disturbance of single-phase distributed photovoltaic, the voltage deviation of all nodes can be estimated as in, are two parts of the voltage sensitivity matrix in equation (3), which respectively represent the sensitivity of node voltage amplitude and phase to reactive power change; Based on equations (7), (8) and (13), equation (12) is converted into the m objective function in, and

[0083] Establishing linearized node voltage constraints and Among them, K 1i and K 2i is the linear approximation constant of the node voltage constraint, E i is the voltage amplitude component at node i, F i is the voltage phase component at node i, is the maximum permissible value of the square of the voltage at node i, is the minimum permissible value of the square of the voltage at node i;

[0084] Based on the relation (14), the objective function of the quadratic problem of optimal reactive power output of distributed photovoltaic power generation for three-phase voltage imbalance control in distribution network is obtained: Among them, H=ω1H1+ω2H2, is the voltage amplitude sensitivity matrix for reactive power injection at all nodes, is the three-phase voltage unbalance coefficient sensitivity matrix for reactive power injection at all nodes;

[0085] Based on equations (11), (15), (16) and (17), a convex optimization model of power optimization control for three-phase voltage imbalance management in distribution network is constructed. The convex optimization model of power optimization control for three-phase voltage imbalance management in distribution network is solved to obtain the optimal reactive power output of distributed photovoltaic power generation.

[0086] Among them, the convex optimization model of power optimization control for three-phase voltage imbalance management in distribution network is solved to obtain the optimal reactive power output of distributed photovoltaics, including:

[0087] Based on the optimization algorithm, the convex optimization model of power optimization control for three-phase voltage imbalance management of distribution network is solved. If the VUF of all three-phase nodes after optimization cannot meet the preset requirements, the weight factors ω1 and ω2 are updated until the VUE of all nodes meet the preset requirements, and the optimal reactive output of distributed photovoltaic is obtained. The reactive power dispatch instruction is sent to the photovoltaic inverter controller, and the three-phase voltage imbalance management is achieved through the reactive power generated by the photovoltaic inverter.

[0088] like Figure 2 As shown, the power control system for managing three-phase voltage imbalance in a distribution network provided by an embodiment of the present invention includes:

[0089] The three-phase power flow calculation module 100 is used to calculate the three-phase power flow of the distribution network, obtain the Jacobian matrix, and determine the relationship between the power change of each node and the voltage amplitude and phase change. in, is the Jacobian matrix, ΔP is the active power change of each node, ΔQ is the reactive power change of each node, ΔE is the voltage amplitude change of each node, and ΔF is the phase change of each node;

[0090] The three-phase voltage unbalance coefficient sensitivity matrix acquisition module 200 is used to substitute the relationship (1) into the relationship between the change ΔVUF of the three-phase voltage unbalance coefficient and the change ΔV of the voltage at all nodes: Get the three-phase voltage unbalance coefficient sensitivity matrix in, is the three-phase voltage unbalance coefficient sensitivity matrix for all node voltage changes, is the three-phase voltage unbalance coefficient sensitivity matrix for all node active power and reactive power, and The three-phase voltage unbalance coefficient sensitivity matrix corresponding to active power and reactive power injection of all nodes respectively;

[0091] The three-phase voltage unbalance coefficient sensitivity matrix simplification module 300 is used to assume that the active power injected by the single-phase distributed photovoltaic in the distribution network is constant and only the reactive power of the single-phase distributed photovoltaic can be controlled, and simplify the relationship (3) to Where ΔQ is the reactive power injection of all nodes;

[0092] The three-phase voltage unbalance coefficient sensitivity matrix conversion module 400 is used to establish the relationship between the reactive power injection of all nodes and the reactive power injection of single-phase distributed photovoltaics: ΔQ=DΔQ DER (5); where ΔQ DER is the reactive power injection of all single-phase distributed photovoltaics, and D is N showing the connection relationship between single-phase distributed photovoltaics and nodes. T ×N d Incidence matrix, N d is the number of single-phase distributed photovoltaics, N T is the number of single-phase nodes; Substituting equation (5) into equation (4), we get the relationship between the change vector of the three-phase voltage unbalance coefficient and the reactive power injection of single-phase distributed photovoltaics: (6);

[0093] The objective function construction module 500 is used to construct the objective function of the three-phase voltage unbalance coefficient based on the relation (6). Taking the minimum voltage deviation of each node in the distribution network as the optimization goal, the node voltage deviation objective function is constructed Among them, VUF orig is the three-phase voltage unbalance coefficient vector of all three-phase nodes before reactive power injection, p is the phase of the node, ΔV i p is the voltage deviation on a certain phase (p phase) at node i when composite power is injected, and ||·||1 is the Manhattan norm; assuming that the active power injected by the single-phase distributed photovoltaic in the distribution network is constant, and only the reactive power of the single-phase distributed photovoltaic can be controlled, the node voltage deviation and the voltage imbalance coefficient are minimized as the optimization objectives, and the objective function of the optimal reactive output of distributed photovoltaic for the three-phase voltage imbalance management of the distribution network is constructed as minω1J1+ω2J2(9); where ω1 and ω2 are the weight factors of the three-phase voltage imbalance coefficient objective function and the node voltage deviation objective function, respectively;

[0094] The constraint condition building module 600 is used to build the voltage constraint of the distribution network node as Vmin ≤|V i p |≤V max (10): where v min and v max are the voltage upper and lower limits of the distribution network nodes respectively; the reactive power constraint of single-phase distributed photovoltaic is constructed as: In the above formula, and are the upper and lower limits of the reactive power output of single-phase distributed photovoltaics, respectively. DERi is the rated capacity of single-phase distributed photovoltaic, P DERi It is the active power output of single-phase distributed photovoltaic;

[0095] The power control module 700 is used to construct a power optimization control model for the management of three-phase voltage imbalance in the distribution network based on the objective function, voltage constraints and reactive power constraints, solve the power optimization control model for the management of three-phase voltage imbalance in the distribution network, and obtain the optimal reactive power output of distributed photovoltaics.

[0096] Specifically, the power control module 700 includes:

[0097] The non-convex processing unit is used to perform non-convex processing on the power optimization control model for the three-phase voltage imbalance management of the distribution network based on the quadratic convex approximation method, and obtain a new distributed photovoltaic optimal reactive power output objective function for the three-phase voltage imbalance management of the distribution network.

[0098] The objective function conversion unit is used for reactive disturbance based on single-phase distributed photovoltaics. The voltage deviation of all nodes can be estimated as in, are two parts of the voltage sensitivity matrix in equation (3), which respectively represent the sensitivity of node voltage amplitude and phase to reactive power change; Based on equations (7), (8) and (13), equation (12) is converted into the m objective function in, and

[0099] Voltage constraint establishment unit, used to establish linearized node voltage constraints and Among them, K 1i and K 2i is the linear approximation constant of the node voltage constraint, E i is the voltage amplitude component at node i, F i is the voltage phase component at node i, is the maximum permissible value of the square of the voltage at node i, is the minimum permissible value of the square of the voltage at node i;

[0100] The final objective function obtaining unit is used to obtain the objective function of the quadratic problem of distributed photovoltaic optimal reactive output for distribution network three-phase voltage unbalance management based on relation (14): Among them, H=ω1H1+ω2H2, is the voltage amplitude sensitivity matrix for reactive power injection at all nodes, is the three-phase voltage unbalance coefficient sensitivity matrix for reactive power injection at all nodes;

[0101] The power control unit is used to construct a convex optimization model of power optimization control for three-phase voltage imbalance management in distribution network based on equations (11), (15), (16) and (17), solve the convex optimization model of power optimization control for three-phase voltage imbalance management in distribution network, and obtain the optimal reactive power output of distributed photovoltaic.

[0102] Wherein, the power control unit includes:

[0103] A convex optimization model construction subunit is used to construct a power optimization control convex optimization model for three-phase voltage imbalance management in a distribution network based on the above-mentioned equations (11), (15), (16) and (17);

[0104] The power control execution subunit is used to solve the power optimization control convex optimization model for the three-phase voltage imbalance management of the distribution network based on the optimization algorithm. If the VUF of all three-phase nodes after optimization cannot meet the preset requirements, the weight factors ω1 and ω2 are updated until the VUE of all nodes meets the preset requirements, and the optimal reactive output of distributed photovoltaics is obtained. The reactive power dispatch instruction is sent to the photovoltaic inverter controller, and the three-phase voltage imbalance management is achieved through the reactive power generated by the photovoltaic inverter.

[0105] Figure 3 This is a topological diagram of a 13-node IEEE distribution network containing multiple single-phase distributed photovoltaics in an embodiment of the present invention. The location of the single-phase distributed photovoltaics can be randomly selected and can be flexibly arranged at any location in the network. The blue, green, and red colors correspond to the single-phase distributed photovoltaics being connected to the a phase, b phase, or c phase of the corresponding node. Figure 3 The load of node #671 in the distribution network changes, which worsens the unbalanced state of the distribution network (i.e., P La =400kW, P Lb =300kW and P Lc=1040kW), and the three-phase balanced transmission line in the IEEE 13-node distribution network is replaced by a three-phase unbalanced transmission line. For the convenience of calculation, it is assumed that the active power output of all single-phase distributed photovoltaics in the distribution network is the same, such as Figure 4 Among them, except for the period from 11:00 to 14:00, the single-phase distributed photovoltaic active power output did not reach the maximum value, and there was additional reactive power that could be dispatched.

[0106] Depend on Figure 5 It can be seen that the VUF variation within 24 hours at node #692 can be effectively suppressed except for the period from 11:00 to 14:00, because the active power output of distributed photovoltaics has reached its maximum value and no additional reactive power can be dispatched during these time periods.

[0107] Depend on Figure 6 and Figure 7 It can be seen that VUF can be effectively alleviated by reasonably dispatching the reactive power of single-phase distributed photovoltaics. The optimized VUF value is less than 2%, which meets the requirements of IEEE standards. Figure 8 and Fig. 9 It can be seen that regardless of whether single-phase distributed photovoltaic reactive power scheduling optimization is performed, the voltages of all nodes meet the constraints.

[0108] In summary, the embodiment of the present invention is based on the reactive power dispatch of single-phase distributed photovoltaic to manage the three-phase voltage imbalance phenomenon of the distribution network. In the embodiment of the present invention, the power optimization control model for the management of the three-phase voltage imbalance of the distribution network is based on the quadratic convex approximation method for convex optimization and then calculation. This method has a fast calculation time and can be embedded in a real-time application algorithm to achieve short-term reactive power dispatch of a distribution network with multiple single-phase distributed photovoltaics.

[0109] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0110] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0111] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0112] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0113] The parts not described in detail in the embodiments of the present invention are all known technologies to those skilled in the art. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A power control method for managing three-phase voltage imbalance in a distribution network, characterized in that: include: Calculate the three-phase power flow of the distribution network, obtain the Jacobian matrix, and determine the relationship between the power change of each node and the voltage amplitude and phase change in, is the Jacobian matrix, ΔP is the active power change of each node, ΔQ is the reactive power change of each node, ΔE is the voltage amplitude change of each node, and ΔF is the phase change of each node; Substitute the above equation (1) into the equation of the change ΔVUF of the three-phase voltage unbalance coefficient and the change ΔV of the voltage at all nodes: Get the three-phase voltage unbalance coefficient sensitivity matrix in, is the three-phase voltage unbalance coefficient sensitivity matrix for all node voltage changes, is the three-phase voltage unbalance coefficient sensitivity matrix for all node active power and reactive power, and The three-phase voltage unbalance coefficient sensitivity matrix corresponding to active power and reactive power injection of all nodes respectively; Assuming that the active power injected by the single-phase distributed photovoltaic in the distribution network is constant, and only the reactive power of the single-phase distributed photovoltaic can be controlled, the relationship (3) is simplified to Where ΔQ is the reactive power injection of all nodes; Establish the relationship between the reactive power injection of all nodes and the reactive power injection of single-phase distributed photovoltaics ΔQ=DΔQ DER (5); where ΔQ DER is the reactive power injection of all single-phase distributed photovoltaics, and D is N showing the connection relationship between single-phase distributed photovoltaics and nodes. T ×N d Incidence matrix, N d is the number of single-phase distributed photovoltaics, N T is the number of single-phase nodes; Substituting the relation (5) into the relation (4), the relation between the change vector of the three-phase voltage unbalance coefficient and the reactive power injection of the single-phase distributed photovoltaic is obtained: Based on the relationship (6), the objective function of the three-phase voltage unbalance coefficient is constructed: Taking the minimum voltage deviation of each node in the distribution network as the optimization goal, the node voltage deviation objective function is constructed Among them, VUF orig is the three-phase voltage unbalance coefficient vector of all three-phase nodes before reactive power injection, p is the phase of the node, ΔV i p is the voltage deviation on a phase at node i during composite power injection, ||·||1 is the Manhattan norm; Assuming that the active power injected by the single-phase distributed photovoltaic in the distribution network is constant and only the reactive power of the single-phase distributed photovoltaic can be controlled, the objective function of the optimal reactive power output of the distributed photovoltaic for the three-phase voltage imbalance management of the distribution network is constructed with the minimization of the node voltage deviation and the voltage imbalance coefficient as the optimization goal, minω1J1+ω2J2(9); where ω1 and ω2 are the weight factors of the three-phase voltage imbalance coefficient objective function and the node voltage deviation objective function respectively; The voltage constraint of the distribution network node is V min ≤|V i p |≤V max (10): where v min and v max are the voltage upper and lower limits of the distribution network nodes respectively; the reactive power constraint of single-phase distributed photovoltaic is constructed as: In the above formula, and are the upper and lower limits of the reactive power output of single-phase distributed photovoltaics, respectively. DERi is the rated capacity of single-phase distributed photovoltaic, P DERi It is the active power output of single-phase distributed photovoltaic; Based on the objective function, voltage constraint and reactive power constraint, a power optimization control model for managing three-phase voltage imbalance in distribution network is constructed, and the power optimization control model for managing three-phase voltage imbalance in distribution network is solved to obtain the optimal reactive output of distributed photovoltaic.

2. The power control method for three-phase voltage imbalance management in a power distribution network according to claim 1, characterized in that: The method constructs a power optimization control model for three-phase voltage imbalance management of the distribution network based on the objective function, voltage constraint and reactive power constraint, solves the power optimization control model for three-phase voltage imbalance management of the distribution network, and obtains the optimal reactive power output of the distributed photovoltaic system, including: Based on the quadratic convex approximation method, the power optimization control model for the three-phase voltage imbalance management of the distribution network is processed non-convexly to obtain a new distributed photovoltaic optimal reactive power output objective function for the three-phase voltage imbalance management of the distribution network. Based on the reactive disturbance of single-phase distributed photovoltaic, the voltage deviation of all nodes can be estimated as in, are two parts of the voltage sensitivity matrix in equation (3), which respectively represent the sensitivity of node voltage amplitude and phase to reactive power change; based on equations (7), (8) and (13), equation (12) is converted into the objective function in, and Establishing linearized node voltage constraints and Among them, K 1i and K 2i is the linear approximation constant of the node voltage constraint, E i is the voltage amplitude component at node i, F i is the voltage phase component at node i, is the maximum permissible value of the square of the voltage at node i, is the minimum permissible value of the square of the voltage at node i; Based on the relationship (14), the objective function of the quadratic problem of distributed photovoltaic optimal reactive output for three-phase voltage imbalance control in distribution network is obtained: Among them, H=ω1H1+ω2H2, is the voltage amplitude sensitivity matrix for reactive power injection at all nodes, is the three-phase voltage unbalance coefficient sensitivity matrix for reactive power injection at all nodes; Based on the relationships (11), (15), (16) and (17), a convex optimization model of power optimization control for the management of three-phase voltage imbalance in distribution network is constructed. The convex optimization model of power optimization control for the management of three-phase voltage imbalance in distribution network is solved to obtain the optimal reactive power output of distributed photovoltaic power generation.

3. The power control method for managing three-phase voltage imbalance in a power distribution network as claimed in claim 2, characterized in that: The method solves the power optimization control convex optimization model for the three-phase voltage imbalance management of the distribution network to obtain the optimal reactive power output of the distributed photovoltaic system, including: Based on the optimization algorithm, the power optimization control convex optimization model for the three-phase voltage imbalance management of the distribution network is solved. If the VUF of all three-phase nodes cannot meet the preset requirements after optimization, the weight factors ω1 and ω2 are updated until the VUE of all nodes meet the preset requirements, and the optimal reactive output of distributed photovoltaics is obtained.

4. A power control system for managing three-phase voltage imbalance in a distribution network, characterized in that: include: The three-phase power flow calculation module is used to calculate the three-phase power flow of the distribution network, obtain the Jacobian matrix, and determine the relationship between the power change of each node and the voltage amplitude and phase change. (1); among which, is the Jacobian matrix, ΔP is the active power change of each node, ΔQ is the reactive power change of each node, ΔE is the voltage amplitude change of each node, and ΔF is the phase change of each node; The three-phase voltage unbalance coefficient sensitivity matrix acquisition module is used to substitute the relationship (1) into the relationship between the change ΔVUF of the three-phase voltage unbalance coefficient and the change ΔV of the voltage at all nodes. Get the three-phase voltage unbalance coefficient sensitivity matrix in, is the three-phase voltage unbalance coefficient sensitivity matrix for all node voltage changes, is the three-phase voltage unbalance coefficient sensitivity matrix for all node active power and reactive power, and The three-phase voltage unbalance coefficient sensitivity matrix corresponding to active power and reactive power injection of all nodes respectively; The three-phase voltage unbalance coefficient sensitivity matrix simplification module is used to assume that the active power injected by the single-phase distributed photovoltaic in the distribution network is constant and only the reactive power of the single-phase distributed photovoltaic can be controlled, and the relationship (3) is simplified to Where ΔQ is the reactive power injection of all nodes; The three-phase voltage unbalance coefficient sensitivity matrix conversion module is used to establish the relationship between the reactive power injection of all nodes and the reactive power injection of single-phase distributed photovoltaics ΔQ=DΔQ DER (5); where ΔQ DER is the reactive power injection of all single-phase distributed photovoltaics, and D is N showing the connection relationship between single-phase distributed photovoltaics and nodes. T ×N d Incidence matrix, N d is the number of single-phase distributed photovoltaics, N T is the number of single-phase nodes; Substituting the relation (5) into the relation (4), the relation between the change vector of the three-phase voltage unbalance coefficient and the reactive power injection of the single-phase distributed photovoltaic is obtained: An objective function construction module is used to construct an objective function of the three-phase voltage unbalance coefficient based on the relation (6). Taking the minimum voltage deviation of each node in the distribution network as the optimization goal, the node voltage deviation objective function is constructed Among them, VUF orig is the three-phase voltage unbalance coefficient vector of all three-phase nodes before reactive power injection, p is the phase of the node, ΔV i p is the voltage deviation on a certain phase at node i when composite power is injected, and ||·||1 is the Manhattan norm. Assuming that the active power injected by the single-phase distributed photovoltaic in the distribution network is constant and only the reactive power of the single-phase distributed photovoltaic can be controlled, the node voltage deviation and the voltage imbalance coefficient are minimized as the optimization objectives, and the objective function of the optimal reactive output of distributed photovoltaic for the three-phase voltage imbalance management of the distribution network is constructed as minω1J1+ω2J2(9); where ω1 and ω2 are the weight factors of the three-phase voltage imbalance coefficient objective function and the node voltage deviation objective function, respectively. Constraint building module, used to build the voltage constraint of the distribution network node as V min ≤|V i p |≤V max (10): where v min and v max are the voltage upper and lower limits of the distribution network nodes respectively; the reactive power constraint of single-phase distributed photovoltaic is constructed as: In the above formula, and are the upper and lower limits of the reactive power output of single-phase distributed photovoltaics, respectively. DERi is the rated capacity of single-phase distributed photovoltaic, P DERi It is the active power output of single-phase distributed photovoltaic; The power control module is used to construct a power optimization control model for the management of three-phase voltage imbalance in the distribution network based on the objective function, voltage constraints and reactive power constraints, solve the power optimization control model for the management of three-phase voltage imbalance in the distribution network, and obtain the optimal reactive power output of distributed photovoltaics.

5. The power control system for managing three-phase voltage imbalance in a power distribution network as claimed in claim 4, characterized in that: The power control module comprises: A non-convex processing unit is used to perform non-convex processing on the power optimization control model for the three-phase voltage imbalance management of the distribution network based on the quadratic convex approximation method, so as to obtain a new distributed photovoltaic optimal reactive power output objective function for the three-phase voltage imbalance management of the distribution network. The objective function conversion unit is used for reactive disturbance based on single-phase distributed photovoltaics. The voltage deviation of all nodes can be estimated as in, are two parts of the voltage sensitivity matrix in equation (3), which respectively represent the sensitivity of node voltage amplitude and phase to reactive power change; based on equations (7), (8) and (13), equation (12) is converted into the objective function in, and Voltage constraint establishment unit, used to establish linearized node voltage constraints and Among them, K 1i and K 2i is the linear approximation constant of the node voltage constraint, E i is the voltage amplitude component at node i, F i is the voltage phase component at node i, is the maximum permissible value of the square of the voltage at node i, is the minimum permissible value of the square of the voltage at node i; The final objective function obtaining unit is used to obtain the objective function of the quadratic problem of the optimal reactive power output of distributed photovoltaic power generation for the three-phase voltage imbalance control of the distribution network based on the relation (14). Among them, H=ω1H1+ω2H2, is the voltage amplitude sensitivity matrix for reactive power injection at all nodes, is the three-phase voltage unbalance coefficient sensitivity matrix for reactive power injection at all nodes; A power control unit is used to construct a convex optimization model of power optimization control for three-phase voltage imbalance management in a distribution network based on the relationships (11), (15), (16) and (17), solve the convex optimization model of power optimization control for three-phase voltage imbalance management in a distribution network, and obtain the optimal reactive power output of distributed photovoltaics.

6. The power control system for managing three-phase voltage imbalance in a power distribution network as claimed in claim 5, characterized in that: The power control unit comprises: A convex optimization model construction subunit is used to construct a power optimization control convex optimization model for three-phase voltage imbalance management in a distribution network based on the above-mentioned equations (11), (15), (16) and (17); The power control execution subunit is used to solve the power optimization control convex optimization model for the three-phase voltage imbalance management of the distribution network based on the optimization algorithm. If the VUF of all three-phase nodes cannot meet the preset requirements after optimization, the weight factors ω1 and ω2 are updated until the VUE of all nodes meet the preset requirements, thereby obtaining the optimal reactive power output of the distributed photovoltaic.

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